In order to improve the physical and chemical properties of the lubricating oil, a certain amount of additives are added to the lubricating oil to improve its performance; better meet the needs of mechanical lubrication. There are many types of lubricant additives. From the perspective of action, they are mainly divided into two categories. One is to improve the physical properties of lubricating oils, and there are twist index improving additives, oil additives, pour point depressants and antifoaming agents, which can lubricate. Oil molecular deformation, adsorption, solubilization; the other is to improve the chemical properties of lubricating oil, there are extreme pressure anti-wear agents, antioxidants, anti-oxidants, rust inhibitors and detergents, they themselves The lubricating oil reacts. From the mechanism point of view, there are also two types, one is the interface chemistry to achieve the purpose of lubrication, there are additives to improve the carrying capacity (oily agent, anti-wear agent, extreme pressure agent), metal surface passivation agent, rust and corrosion inhibitor , clean dispersing agent, pour point depressant, anti-foaming agent; second, relying on the overall properties of lubricating oil to achieve lubrication purposes, there are antioxidants, stationing agents. Regardless of the classification, lubricating oil additives, except for strange polymers (such as polyisobutylene), are almost always composed of polar compounds.